Green Build Blog: Breathe Easy With Balanced Ventilation

ERVs and HRVs must be able to run at two ventilation rates: the background ventilation rate required to ensure the right number of air changes per hour for the house, and a second, higher rate when the bathrooms and kitchen need a boost. The boost rate is typically 50% higher than the background rate. The background ventilation rate is determined by the home’s exhaust requirement. Depending on whom you ask, this can be determined by the number of bathrooms, the number of occupants, the infiltration rate of the house, and the size of the house—either in isolation or in combination. Recovery-ventilator manufacturers offer guidance for sizing a unit, but the ultimate arbiter is your local building code. Many codes have adopted the American Society of Heating, Refrigeration, and Air Conditioning Engineers’ standard, referred to as ASHRAE 62.2 A standard for residential mechani...